Automatic starting device for electric motors



& 3,549,612

\ Aug. 11, 1925.

P. ROHDE AUTOMATIC STARTING DEVICE FOR ELECTRIC MOTORS Filed March 1.4,1924 nventor Paul Rohcie,

His Attorney.

Patented Aug. 11, 1925.

' barren stares PATENT QEFTCE.

PAUL ROHDE, OF WAIDMANNSLUST, GEEIJIANY, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CQRPORATION OF NEVV' "YORK.

AUTOMATIC STARTING FOR ELECTRIC MOTORS.

Application filed. March .1 1824:.

To all whom it may concern.

Be it known that T, PAUL Ronnn, a citizen of Germany, residing at 1Vaidmann lust, Germany, have invented certain new and useful Improvementsin Automatic Starting Devices for Electric Motors, of which thefollowing is a specification.

My invention relates to dynamo electric macnines and particularly toautomatic starting devices or such machines.

Automatic st devices which operate in response to centrifugal force tocutout resistances have been used to some extent in the past. Thesedevices have been, in most cases, mounted on the sia'l t of the electricmotor and as the speed of the motor in creases operate to cut-outresistance step by step. With this type 01" device special disconnectingcontacts are required for cutting out different sections of theresistance. Such an arrangement is open to the objection that as theresistance is cut-out step by step sparks will form between the contactsand so oxidize them that their conductivity and successful operationwill be impaired. An: other objection to such a device is the dangersattendant on the formation of sparks in dynamo electric machines.

The object of the present invention is to provice a device which willovercome the above objections, be cheap, simple in construction andrender the use of special cutting-out contacts unnecessary,

In carrying out my invention 1 mount a circularresistance element and aresistance shortcircuiting means on the rotatable mem her and arrangethe resistance element and the short-circuiting means relativelyeccentric with reference to the axis of rotation of the'rotatable memberso that the resistance will be progressively short-circuited as thespeed of the rotatable member increases.

For a better understanding of my invention reference may be had to thefollowing descriptions taken in connection with the accompanying drawingin which Fig. 1 is an end elevation partly in section of a start ingdevice built in accordance with my invention, and 2 is a sectional viewtaken along the line 2 2 of Fig. 1.

1n the accompanying drawing, a casing. 10 is shown mounted upon a shaft11 adapted to rotate therewith. Mounted eccentrically within the casing10 is a substantially cir cular helical resistance element 12 and adja-Serial No. 699,291.

cent to, and outside oi the helical resistance element 12 are twoconcentrically arranged semicircular members 13 which are adapted toprogressively short-circuit the helical resistance element 12 as it isthrown outwardly due to centrifugal force as the speed of the rotatablemember increases. The ends of the helical resistance element 12 arecarried through the casing 10 and are provided with erminal connections14. Equally spaced about the casing 10 and within the circularresistance element 12 are located insulating rollers 15 which supportthe helical resistance element 12-. These insulating rollers 15 aremounted upon rods 16 which are adapted to move radially within elongatedslots 17 formed in the side of the casing 10. The slots 17 are 01"-different lengths, their outer ends being located on a line concentricwith the axis of rotation and the inner ends being located along a lineeccentric with the axis of rotation. The slots 17 are arranged radiallywith respect to the shaft 11 so that the insulating rollers 15 can moveoutwardly and maintain contact with the helical resist ance element 12as it moves outwardly due to centrifugal action. These insulatingmembers, because of their weight, also act to cause the helicalresistance element 12 to move outwardly. The weight of the rollers 15can be varied to produce different degrees ;of sensitiveness oradditional weights might be added at the ends of the rods 16. In somecases the rollers 15 may be fixed, and the resistance element 12 aloneallowed to move outwardly by reason of its own weight and centrifugalforce. In operation, the centrifugal force exerted upon the helicalresistance element 12 and the rollers 15 due to the speed of therotatable member will cause the circular resistance to expand and engagethe semi-circular members 13. This construction produces a gradualrolling of the resistance coils into contact with the short circuitingmembers 18 which are arranged adjacent thereto. The expansion of thecircular resistance results in progressively cut ting-out the resistancesince the successive portions of the resistance gradually andprogressively press against the contact plates and thus produce anincreasing short-circuiting of the helical turns along themselves.

The return of the helical turns of the expansible resistance into theiroriginal position as the centrifugal :torce decreases is caused eitherby their own elasticity or by any suitable spring action which might beprovided.

In Fig. 2, there are shown two helical resistance elements 12, one foreach phase of a two phase induction motor of the wound rotor type. Idesire to have it understood, however, that any number of helical resistance elements might be provided depending upon the particularapplication and the number of phases of the motor. It should also beunderstood that the helical resistance elements can be arrangedconcentric and the short-circuiting means eccentric with the axis ofrotation and that many other modifications might be made withoutdeparting from the spirit and scope of my invention.

hat I claim as new and desire to secure by Letters Patent oi the UnitedStates, is:

1. In a dynamo electric machine, a rotatable member, a staring device onsaid rotatable member comprising a substantially circular resistanceelement surrounding said rotatable member, and a substantially circularshort circuiting element surrounding said rotatable member and normallyeccentrically arranged with reference to said current resistanceelement, the inner one of said elements being expansible and supportedto permit engagement with the outer member forprogressivelyshort-circuiting portions of said resistance element as'the speed ofsaid rotatable member increases.

2. In a dynamo electric machine, a rotatable member, a starting deviceon said member comprising an expansible substantially circularresistance. element movably supported around said rotatable member andeccentrically arranged with reference to the axis of rotation of saidrotatable member, and means for progressively short-circuiting portionsof said resistance element as the said resistance element expands whenthe speed of said rotatable member increases.

3. In a dynamo electric machine, a rotatable member, a starting deviceon said member comprising a helical resistance element movably supportedin substantially circular form around said rotatable member, and asubstantially circular contact member surrounding said resistanceelement and supported ecccntrically thereto for progressivelyshortcircuiting portions of said helical resistance element as the speedof said rotatable member increases.

l. In a dynamo electric machine, a rotatable mei'uliier, a startingdevice on said member con'iprising an expansible substantially circularresistance element surrounding said rotatable member, movable supportsfor said resistance element adapted to move radially with said elementas the speed cl said rotatable member increases, and a substantiallycircular contact member surrounding said resistance element andsupported eccentrically thereto tor progre 'ively short-circuit ingportions oi said resistance clement upon the expansion of said circularresistance element.

5. In a dynamo electric machine, a rotatable n'iember having radialslots of ditl'ercnt relative lengths formed therein, astarting device onsaid member comprising an expansible sulistantially circular resistanceelement eecentrically arranged with reference to the axis of rotation ofsaid rotatable member, movable weights for supporting said resistanceelement-mounted within said slots and adapted to move radially with andexpand said resistance element as the speed of said rotatable memberincreases a substantially circular contact member surrounding saidresistance element and supported eccentrically thereto :torprogressively short cireuiting portions of said element upon theexpansion thereof.

In witness whereof, I have hereunto set my hand this 21st day ofFebruary 192st.

PAUL ROHDE.

